Magnesite ore treatment



Patented Nov. 2-1, 1944 MAGNE SITE ORE TREATMENT Arthur J. Weinig, Golden, (3010., assignor to Basic Magnesium, Incorporated, Las Vegas, Nev., a corporation of Nevada Drawing. Application April 26, 1943,

Serial N0. 484,633

25 Claims. (01. 209-166) This invention relates to the froth flotation treatment of magnesite ores for the recovery of the magnesite content of the ore separate from other ore constituents.

The present application contains subject matter related to the disclosures in the following 00- pending applications I have filed:

Serial No. 394,851, filed May 23, 1941, for Separation of magnesite ore constituents; Serial No. 430,619, filed February 12, 1942, for Treatment of magnesite ores; Serial No. 458,323, filed September 14, 1942, for Flotation of magnesite; and

satisfactory, but when lower grade ores are sub-- jected to froth flotation, the methods heretofore known are not effective in making a prodnot of the prescribed grade.

Serial No. 474,982, filed February 6, 1943, for

Froth flotation treatment of low grade magnesite ores.

Features described but not claimed herein have been made the subjects matter of claims in my aforesaid applications. In addition, the present application claims certain features partially disclosed in the first mentioned application, but which could not be claimed in said application without introducing new matter therein, and as to such features the present application is a substitute for said earlier filed application.

Magnesite ores occur in numerous deposits, such as the one at .Luning, Nevada, and consist of magnesium carbonate compositions containing as contaminants one or more of the follow- .ing; dolomite, serpentine, forsterite, hydromag- For certain industrial purposes, a product of suitable market grade will contain not to exceed 1.5% CaO and not to exceed 0.75% insoluble.

When relatively high grade ores are treated, various methods may be employed to bring the final product within the desired grade. of these, froth flotation concentration has proved highly .In my earlier investigations, I have discovered that the magnesite content of such magnesite ores can be separated cleanly from, limebearing constituents such as dolomite, or insolubles such as serpentine, by forming a colloidal metallic hydroxide precipitate in the pulp of the treatment by the reaction of certain types of metallic salts with the lime-bearing minerals in the circuit.

This colloidal precipitate which I have chosen to calla non-acid hydrogel acts as a depressant for the lime-bearing and other contaminant matter permitting various collector reagents to function eificiently in such a pulp and concentrate the'magnesite content in the pulp with only a nominal amount of lime and insoluble constituents present.

A variety of metallic salts were tested and found to be satisfactory for this purpose. In general, salts of iron, tin and aluminum were quite satisfactory, and where the alkalinity of the circuit did not afford sufficient material for r the above reaction, I added caustic, such as caus- Because of grade.

these, certain frothers were employed in some tests and pine oil and synthetic alcohol composttions were found to be well suited for this purpose.

Further investigations led to the discovery that fractionation flotation would afford a recovery of a substantial percentage of the magnesite content/ Qne typical test operation will suffice to illustra c this stage of the development. The ore taken for test was from a Luning, Nevada deposit and analyzed as follows:

Per cent analysis Insoluble OaO MgO 1 Chalky white vein matter 4. 16 39. 45 2 White crystalline vein matter.. 0. 24 47. 27 3 Dark gray crystalline vein matter 0. 0. 56 46. 87 4 Ore as taken for test 2. 04 1. 76 44. 60

Percent analysis Weight x 25 Insol. :10

It will be noted that the ore taken for the aforesaid test was of relatively-high grade and the formation of the hydrogel alone was suflicient to depress enough of the lime and insoluble content to permit recovery of a substantial proportion of the magnesite content ofdesired However, when lower grade and more mineralogy complex ores are subjected to treatment, other means of inhibiting the flotation of undesirable constituents must be provided to hold' the lime and insoluble content of the concentrate within prescribed limits.

Thus, in my application Serial No. 430,619 I disclosed that beneficial results could be obtained by the inclusion in a treatment of the above described character of a molecularly dehydrated phosphate or salt of phosphoric acid. Tetra a1- kali pyrophosphate compositions and alkali tetraphosphates were cited as classes of compositions suitable for this purpose.

In addition, this application disclosed that the caustic of the treatment might be either a hydroxide, or a basic salt; the latter term being used in the sense of having the base-forming constituents present in excess of the proportion necessary for a normal compound. It was disclosed additionally that an alkali circuit was not essential as good results were obtained with a -pH of 6 or slightlyv higher,

provided basic salts or hydroxides are formed. The pyrophosphate compositions were found to be particularly eifective in retarding the passage of contaminant slimes into the froth and since such slimes are frequently formed in substantial quantities in milling operations of this character, the lesser amount of the slimes entering the concentrate not only improved grade and recovery but had the added benefit of maintaining the circuit in a condition of efilcient equilibrium.

The next phase of the development came about as a result of war shortages. nut oil soap and palm kernel oil soap were cut off necessitating substitution of other collector reagents in the operations hereinbefore described. The class of compositions designated generally as naphthenic acids and salts thereof comprising any one or combination of non benzenoid cyclic carboxylic acids derived from petroleum were investigated, and found to give highly satisfactory results.

Again when such reagents were used,.the nonacid hydrogen was formed by reacting the metallic salt with'alkaline material of the circuit and preferably a pyrophosphate composition was used in conjunction therewith to offset the tendency of the naphthenic acid collector to carry first of these tests, ore from ,a Luning, Nevada deposit was crushed to a 5 inch maximum size and passed over a 2 /2 inch screen. The part of the ore 'not passing the screen was handpicked and the low grade portion was remixed with the minus 2 /2 inch portion.

' This mixture containing a relatively high proportion of slimy contaminant, was ground to -l00 mesh. A suitable pulp was formed of the ground product and subjected to froth flotation with the following reagents:

Lbs. per ton Aluminum sulfate 8.4 Caustic soda 2.62 Laurie acid 3.14

The pH of the pulp. after addition of the reagent was determined as 8.3. Thepilot mill results of the tests are shown below:

Percent Percent Percent Pmduct of feed insol. CaO

In the next test the ore taken for treatment was ore from the Margie claim, Luning, Nevada,

assaying 2.21% insoluble and 4.41% CaO, and was ground to 100 mesh. A'pulp was formed and conditioned with 8 lbs. ferric chloride, 1.5 lbs. tetrasodium pyrophosphate and 1.6 lbs. of #270 naphthenic acid per ton of ore treated. I

This mixture, after the initial conditioning,

' was subjected to froth flotation and a recovery of was obtained. Th'e concentrate analyzed 0.91% insoluble and 1.23 CaO. It should be noted that although the ore taken for thistest was relatively low grade, the concentrate formed Supplies of cocoin the operation contained considerably less than the prescribed limits of impurities.

The next phase of the development involved the separation of high grade magnesite from dolomite and low grade magnesite constituents of a magnesite ore. To accomplish this result, a hydogel is formed in the pulp in the manner hereinbefore described. A pyrophosphate composition is used as a depressant for the lime content, and starch is added to depress the insoluble and gangue content which tends to collect in the froth under the action of the naphthenic acid or lauric acid collector reagent.

The details of the aforesaid operation are described in my copending application, Serial No. 474,982, and represent the culmination of my developments in the treatment of magnesite ores, rior to the present invention. 7

While the aforesaid methods are effective in the treatment of many grades of magnesite ores, they will not produce the desired grade of concentrate when certain low grade ores are treated. The present invention resides in the discovery that silicic acids may be used in conjunction with such treatments to produce a highly selective froth of low volume with flotation of lime-bearing minerals and gangue slimes effectively retarded.

It is an object of the Present invention to provide a simple, economical and efficient method of concentrating the magnesite content of magnesite ores in an action in which only fractional amounts of insoluble and ganguematter collect in the concentrate.

Another object of the present invention is to provide a froth flotation treatment for magnesite ores in which reagent costs are substantially reduced without impairing metallurgical efliciency.

Other objects reside in novel steps and treatments, the details of which will be explained in the course of the following description.

A typical treatment embodying the features of the present invention involves the use of the following preferred reagent combination, designated in pounds reagent per ton of ore:

,-(a) Salts of aluminum and iron, such as aluminum sulfate and ferric chloride--3 to 16 lbs/ton;

l (b) Naphthenic acids or lauric acids- 0.3 to 4 the pulp preferably ahead of the flotation circuit,

and are conditioned by agitation until reaction is complete. In this operation the salts are decomposed by the lime-bearing mineral grains of theore, resulting in a surface deposition on such grains of hydrates of the metals in the salts. In this reaction, aluminum and iron are precipitated out of solution and equivalent amounts of lime are rendered soluble.

The effect of the reaction is to prevent the flotation of lime-bearing minerals by the inhibiting effect of the deposited hydrate. More specifically, such salts have been found to possess special affinity for dolomite, calcite and similar h '3 calcareous materials, but have no afflnity for magnesite. The reaction apparently proceeds according to the following equation:

The naphthenic acids and lauric acids recommendedfor this treatment function in the pulp as both frothing and collecting agents. They exert a strong flotation effect on themagnesite ore constituents and will float calcite and dolomite readily as well as gangue materials unless said constituents aresubjected to satisfactory inhibiting influences. Consequently, when the hydrate deposit is formed on the lime-bearing mineral surfaces, the reagents function to produce a desirable concentration, particularly when the ores are of relatively high grade.

As the ores :become poorer in grade, it .will be necessary to further depress or exert a flotation inhibiting effect on the gangue and lime-bearing minerals. To assist 'in this action, the tetra alkali pyrcphosphate compositions are introduced in the pu1p conditioning stage and further inhibit the flotation of lime-bearing constituents. However, these compositions have some tendency to cause flotation of gangue matter and insoluble silicates.

Consequently, when an ore of relativel low grade contains substantial quantities of insoluble silicates, it is necessary to add to the reagents hereinbeiore'designated, some additional agent which will inhibit the flotation of the siliceous material. Causticized starch was found to be an eifective addition agent for this purpose. It overcomes the flotation tendency of mineral silicates due to the presence of tetra alkali pyrophosphate and also reduces the toughness and volume of froth. For many flotation treatments the combination of the aforesaid reagents is ample to attain thedesired results. 7

However, when still lower grade ores are to be treated and the aforesaid reagent combination will not produce satisfactory results, a concentrate of prescribed grade can be attained by "including silicic acids as an additional reagent in the treatment. More specifically, the silicic acid composition should be a polymerized acid which is not an ionized salt, or acid orgel. Preferably, such composition is produced by exactly neutralizing alkali silicates with aging. l

The inclusion of the silicic acids in the treatment thus provides a, low cost reagent which is effective in producing a highly selective: froth of low volume. Itaids in retarding the flotation of lime-bearing minerals and gangue slimes and gives improved recovery and grade in the magnesite concentrates. Further, in many treatments it will supplant the use of the tetra alkali pyrophosphate.

A typical test operation will illustrate the advantage gained by introducing a quantity of silicic acid into the treatment. A sample of Gabbs Val- I ley ore ground dry to pass through mesh and containing 20% plus 200 mesh by weight was used in the test. The analysis of the ore was as follows:

500 grams of the ore mixed with 2.5 grams alumineral acid and then minuin sulfate was agitated in a laboratory niechanical type flotation machine with 2 liters of water heated to 130 F. This yielded a pulp at 9.

Tssr B lsranmnoltnecm Comma-non) Reagents'used (equivalent lb. per ton of head ore) temperature of 100 F. Other reagents were added to .the pulp'in the following order: 1) mm.

causticized starch, (2) silicic acid. (3) tetrasoin all. m 1 dium pyrophosphate, and (4) naphthenic acids. FLK 1715 &2 m After one minute conditioning, air was ad- Silicic ecid- M 11 h to.. mitted to the cell and froth drawn off for two iti g d di l a 3%. 39,: minutes. The slimesfrom the concentrate were Weight Analysis Product Percent (Jumper-cant G. Percent g Insol. 000 R10; Insol. C50 B:

151: cleaner mm; 203 52.0 52.0 .58 1.41 .46 .58 1.41 .40 2nd cleanerfroth- 27 5.4 58.0 .97 3.25 .54 .00 1.07 .47 Oleanertailing.- 80 17.8 75.8 3.04 10.37 .100 1.29 11.04 .01 Rougher tailing 121 24.2 100.0 9.38 12.92 2.98 3.25 5.89 1.18

returned to the machine and after mixing, a sec- In order to illustrate the effect of silicic acid 0nd froth was drawn off for one and one-half W in the aforesaid treatments, the same ore was minutes. This procedure was repeated two more treated under smu' lar conditions using the same times and the slime from the last frothing operacombination of reagents except that silicic acid tion was not returned to the machine. was omitted. The results of this testing are set The rougher concentrate was returned to the forth in the followm' gtabulation: machine with the water decanted from the rough-.

Trzsr C (SILICIC Acrn m'rrnn er tailmg and after the addition of necessary re- 30 0 agents was subjected to cleaning for from five to Reagents used (equivalent lb. per ton. of head six minutes. Whenever it was desired to raise ore) the froth level, the nearly clearwater was decanted off the concentrates and returned to the Roughing Cleaning machine.

The silicic acid of the treatment was prepared 10.0 None by the addition of 1.8 ml. sulfuric acid to .gg g ggg g Starch 3: 10 ml. water glass (41 B. Ratio NazO to $02 1 a...msod ia'etia hos hm 0.6 0% to 3.25) diluted to 200 ml. with water and aged 40 Nflphthemc fields None for four to five days before use.

Weight Analysis Product Per cent Cum. per cent G. Percent g 111501. QaO R101 Insol.| 000 I 11,0,

1st cleaner froth 170 35.0 35.0 0.82 3.04 .52 .82 3.04 .02 2nd cleaner frotl1 '93 18.5 54.1 0.80 2. ll .50 .81 272 .52 Cleaner tai1ing 109 21.7 75.8 2.20 6.12 .30 1.23 3.70 .62 Rougher tailing 122 24.2 24.2 8.98 12.70 2.88 3.10 6.87 1.17

The test results follow: The peculiarity of this test is that the second froth is of better grade than the first one. D Tnsr A (STANDAR REAGENT COMBINATION) Thls 1s probably due to the fact that the first Reagents used (equivalent lb. per ton of head ore) froth contained more low grade slime.

\ Roughing Cleaning Aluminum sulfate h 10.0 Causticized starch-.. 4 0 4 gilitcic agid fi fi t I 1.4 0. 4

e raso rum to OS Napthenic am d 3. f l $3 Bf Weight I Analysis Product Per cent Cum. per cent G. Per cent g Insol 0110 R20; Insol. CaO R10;

1st cleaner froth 275 55.4 55,4 .47 1.40 .44 .47 1.49 .44 2nd cleaner froth 7.0 62.4 .79 2.31 .56 .51 1.59 .45 Cleaner t 20.3 82.4 3.74 14.77 1.18 1.31 4.34 .63 e i z. 17.3 100.0 12. 52 10.07 4.12 3.24 5.84 1.21

Tss'r D (Tmrmsonmu PYBOPHOSPHATE Omr'rsn) Reagents used (equivalent lb. per ton oj'head (3) 2d cleaning (with pyro and other gangue depressant) eliminated 78% insoluble and 71% of the lime content of the first cleaner conconcentrate.

v 078) centrate.

, The ratio of insoluble elimination to lime Rou hing Cleaning elimination in successive operations is then as follows: lt'gfi'etigitiffizi: 2 3:2 tfi fl sh g P ccacr 0.4 S ceanmg pyro aone 'ifiifiitifstt attsif fffffiiijii:::::::::: t??? $132 2d cleaning (pm with other depressentsh- These figures confirm the general impression Weight Analysis Product Per cent Cum. per cent G. Per cent g Insol 0210 R: Insol. 080 11,0,

1st cleaner froth; 53. 4 53. 4 47 l. 49 42 47 1. 49 42 2nd cleaner froth- 5. 2 58. 6 82 3. 49 42 49 l. 67 42 Oleanertailin 18.8 71.4 3.82 12.92 1.06 1.31 4.40 .51 Roughertailing 113 22.5 100.0 9. 72 10.01 3.21 3. 21 5.82 1.17

In order to summarize the results of the pre- 9 gained from an earlier test that. tetrasodium ceding tests A, B, C and D, the grade of acoupyrophosphate is very effective as a lime decentrate containing 55% of the headsby weight pressant. but may promote certain gangue minhas been calculated by interpolation. erals. When used in conjunction with starch and silicic acid this tendency is not manifest Analysis r concentrate by inand no difliculty was experienced in meeting the 5221531313011 [or 55% weight insoluble specifications with the Gabbs Valley ore, the weight recovery obtainable being lim- Insol CaO R20 ited by the maximum permissible lime content of the concentrate rather than by the msolu- ...b1e content.

fzr i r i oitfii1d $ffi 0.53 1.48 0.45 In order to demonstrate that ferric chloride @gigggiggfigffggfjgfilmay be substituted for aluminum sulfate, certed (test D).......... 1.55 0.42 tain test operations are being cited. In the tests the following procedure was adopted:

In order to bring out the effect of the tetra- 4 Five hundred grams of Ore were agitated in a sodium pyrophosphate on the various classes of laboratory machine of mechanical type with two gangues, the following test (E) is reported in liters Water heated and reagents which two cleaning stages were employed. were added t0 the P in the following Order:

. l (l) ferric chloride, (2) causticized starch, (3)

TESTE 5 silicic acid, (4) tetrasodium pyrophosphate, (5) Reagents used (equivalent lb. per ton of head lauric acid- Ore) After one minute conditioning a1r was admitted to the cell and froth was drawn off for two 2nd minutes. lihe slimes from the concentrate were 7 Roughmg cleaning cleaning 50 decanted back into the machine and after mixing, a second froth was drawn oif for 1.5 min- Aluminum sulfate. 10.0 None None utes. This procedure was repeated two more Smelt-1 2 times, the slime from the last (or fourth) froth- 'letrasodiurn pyropliosphate. I new M ing operation not being returned to the machine. Naphthenic acids 0.58 0.22 0.36 The mean temperature during roughing W315 Weight Analysis Product Per cent Cum. per cent G. Percent gh Insol. 080 R203 Ins l. CaO Rio.

C1e8n'ertroth 212 42.4 42.4 0. 31 1.15 0.40, 0.31 1.16 0.4 2d cleaner tailing. 24.0 66.4 1.88 5.07 0.84 0.87 2.68 0. 56 1st cleaner tailing--. 91 18.2 84.6 2.84 13.80 1.20 1.30 5.00 0.70 Rougher tailing 77 15. 4 100. 0 13.64 10. 43 4. 82 3. 19 5. 84 1. 33

The relative amountsof insoluble and lime The rougher concentrate was returned to the gliminatedlby each bsuccessive flotationstep have 70 a hin with the water decanted from the can ca to e as follows: her tailing and after the addition of neces- (1) Roughing (without pyro) eliminated 66% mug insoluble and 28% lime from the head ore. my teagents summed cleanm? for me (2) 1st cleaning (with 'pyro alone) eliminated six m Whenever e deslred lu le and 59% lime from the rough r "r the froth level, the water decanted off the concentrates was returned to the machine.

The results of these tests follow:

Reagents (equiv. lb. per ton of ores) weight analysis (per cent) Test No. l Product Silicic Sodium Lauric FcCl; Starch acid Pym acid G. Per cent 1111101. C Ra0,

M STANDARDREAGENTCOMBINATION Concentrate..... 220 459 0.02 1.10 0.30 0.4 0.2 C1.tailing. 112 225 2.54 7.70 0.55 0.4 1.4 0.0 0.92 a. tailing 157 31 0 7.30 10.45 2.54 Heads 497 3.17 5.54 1.10

N STANDARD REAGENT COMBINATION 1st froth 284 57.1 0.02 1.70 0.43 2d ir0th.. 2a 4.0 0.00 2.55 0.40 0.4 0.1 CLtailing. 75 15.1 0.75 13.00 1.12 10 0.4 1.4 0.0 1.15 R.taiiing 115 23.2 8.86 11.85 3.10

Heads 497 3.03 5.80 1.18

0 SODIUM PYROPHOsPHATE OMITTED Concentrate..." 248 49.0 0.00 1.77 0.20 0.4 0.4 None. 01. tailing 120 25.2 2.44 8.85 0.86 10 0.4 1.4 None 0.40 R. tailing 120 25.2 ass 10.90 0.00

Heads 500 3.20 5.84 1.10

P CAUSTICIZED sTARcH OMITTED 40.1 0.71 2.15 0.00 10. 3 1. a. 0. 45 None 0.2 0.2a Cl.tailing 11.7 4.10 11.00 1.30 10 None 1.4 0.0 0.57 R. tailing 114 22.9 9.22 10.00 3.12

Heads 497 3.14 5.51 1.1:;

Q, CAUSTIOIZED sTARcH OMITTED Ooncentrate 270 54.3 0.90 2.42 0.40 None 0.2 c1. tailing 92 18.6 2.04 7.70 0.90 10 None 1.4 0.0 0.86 R. tailing 105 27.1 0.04 11.20 2.00 3.14 5.70 1.15

R SILICIO ACID OMITTED 1st froth 227 45.5 0.70 1.07 0.44 I an th 8.4 1.20 2.08 0.54 0.4 None 17.0 2.72 9.88 0.86 10 0.4 None 0.0 0.09 29.1 7.54 11.00 2.00

Ascompared with operations in which naphthenic "a'C'id' WaS the collector reagent, the use of tainable with naphthenic acid. The function of the two'reagents was shown to b essentially similar, and omission of each of the three modifying agents (causticized starch, silicic acid and sodium pyrophosphate) resulted in a substantial low.-

ering of the efficiency of the separation. that in other operations sodium silicate has been Lauric acid produces a tougher but less volumused in the treatment of magnesite ores to form inous froth than is produced by naphthenic acid, a Silica gel in the pulp which precipitates on and the efiect of silicic acid as a froth controlquartz, serpentine and calcite constituents to deling reagent is less apparent. However, the omispress them. In the present treatment such con sion of silicic acid from the reagent combinaditionis undesirable and productive of detrimention results in alowering of recovery by some .tal results, for which reason I have specified 10% for a given grade of concentrates. herein the essential character of the silicic acid The use of iron salts furnishes additional evitaken for treatment. dence of the precipitatingaction on lime-bearing A series of tests were undertaken to determine minerals by coloring these minerals in the flotaj st what characteristics d p operti s of the tion tailings m'th a clearly visible rusty stain." silicic acid would give the desired results. In The magnesite in the concentrate is unstained; the testing, numerous inconsistencies were noted From the foregoing description of test proceand after eliminating several possible causes, it (lure, it l be pparent that good recoveries will was determined that the elapsed time between be attained, even when relatively low grade ores are treated, by following the practice of the present invention. 'Where practical," substitute ingredients have been provided in the reagent combination so that benefit can be taken of price .fluctuations or operations continued in the face combination becomes important. I am aware the preparation of the silicic 'acid reagent and pulp body, and inhibiting notation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch and polymerized silicic metallurgical results. Other tests demonstrated I the present invention, I have found that best results are obtained in the treatment'when the silicic acid is used in an amount between 0.5 and 3 pounds per ton of ore treated.

The action of the silicic acid composition in the treatment is particularly effective in depressing dolomite, although its functions effectively with other materials such as serpentine, forsterite, hydromagnesite and the like.

The large number of test operations described herein affords a standard of selection of reagent combinations to suit the properties of a given ore taken for treatment. Where reagent ingredients have been described without citation of specific operating data. it will be understoodthat they are usedand function in the treatment in substantially the same way as other ingredients for which they are substitutes.

Changes and modifications may be availed of within the spirit and scope of the invention as defined inthe hereunto appended claims.

What I claim and desire to secure by Letters Patent is:

1. The method of concentrating magnetic ores which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit a hydrate of the metal on the surfaces ofsaid ,lime-beari"g mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentratethe magnesite content of the ore in a frothat the surface of the .pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch and silicic acid present in said pulp.

2. The method of concentrating magnesite ores,

which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp,introduc. ng a salt selected from the group consistingof salts of aluminum, tin and iron into said pulp to react with lime- .bearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of said lime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentrate the magnesite content of the ore in a froth at the surface of the til acid present in said pulp.

3. The method of concentrating magnesite. ores,

which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to forma pulp, introducing a salt selected from the group'consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of saidlime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentrate the magnesite content of the ore in a froth at the surface of the pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch, tetra alkali pyrophosphate, and silicic acid present in said pulp.

4. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a 'liquidcarrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with lime- .bearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of said lime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of o1eic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentrate the magnesite content of the ore in a froth'at the surface of the pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch, tetra alkali pyrophosphate and polymerized silicic acid present in sai pulp.

5. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit a hydrate of the metal on thesurfaces of said lime-bearing mineral, and subjecting such pulpto a froth flotation treatment during which causticized starch,

silicic acid, tetra alkali pyrophosphate and anaphthenic acid collector are successively entered into the pulp.

6. The method of concentrating magnesite ores, which comprises introducing'magneste ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of'said lime-bearing mineral, and subjecting such pulp into a froth flotation treatment during which causticized starch, silicic acid, tetra alkali pyrophosphate and a lauric acid collector are successively entered into the pulp.

'7. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected fromthe group consisting of salts of aluminum,

tin and iron into said pulp to react with limebearing minerals of the pulp and deposit a hydrate of the metal on the surfaces of said limebearing minerals, and subjecting-such pulpto a froth flotation treatment during which caustic starch, silicic acid, and a naphthenic acid collector are successively entered into the pulp.

8. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing minerals of the pulp and deposit a hydrate of the metal on the surfaces of said limebearing minerals, and subjecting such pulp to a froth flotation treatment during which caustic starch, silicic acid, and a lauric acid collector are successively entered into the pulp. I

9. In the art of concentrating magnesite ores, in which the magnesite content of an aqueous magnesite ore pulp is collected on the sur-' face of the pulp by the action of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts in a froth flotation treatment, the improvement which comprises conditioning such magnesite content for selective collection by the reagent in an alkaline medium having a pH of at least 8 by reacting the limebearing content of the pulp with a salt selected from the group consisting of salts of aluminum, tin and iron to deposit a hydrate of the metal on the surfaces of the lime-bearing constituents which hydrate prevents such constituents from responding to the action of said collector reagent.

10. In the art of concentrating magnesite ores, in which the magnesite content of an aqueous magnesite ore pulp is collected on the surface of the pulp by the action of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts, ina froth flotation treatment, the improvement which comprises conditioning such magnesite content for selective collection by the reagent in an alkaline medium having a pH improvement which comprises conditioning such magnesite content for selective collection by the reagent in an alkaline medium having a pH'oi at least 8 by reacting the lime-bearing content of the pulp with a salt selected from the group consisting of salts of aluminum, tin and iron to de. posit a hydrate of the metal on the surfaces of the lime-bearing constituents which hydrate prevents such constituents from responding to the action of said collector reagent, and continuing said conditioning treatment until the reaction of th metallic salt iszcomplete, before subjecting said pulp to froth flotation.

13. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing aluminum sulfate into said pulp to react with lime-bearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of said lime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentrate the magnesite content of the ore in a froth 'at the-surface of the pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch and silicic acid present in said pulp.

14. The method of concentrating magnesite ores, which comprises introducing magnesit'ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing ferric chloride into said pulp to react with lime-bearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of said lime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts to concentrate the magnesite content of at least 8 by reacting the lime-bearing content of the pulp with aluminum sulfate to deposit a hydrate of the metal on the surfaces of the lime-bearing constituents which hydrate pre vents such constituents from responding to the action of said collector reagent.

11. In the art of concentrating magnesite ores, in which the magnesite content of an aqueous magnesite orepulp is collected on the surface of the pulp by the action of a collector reagent selected-from the group consisting of oleic, palmitic,

stearic, capric, lauricand naphthenic acids and their salts, in a froth flotation treatment, the improvement which comprises conditioning such magnesite content for selective collection'by the in which the magnesite content of an aqueous magnesite ore pulp is colected 0n the surface .of the pulp by the action of a collector reagent seof the ore in a froth at the surface of the pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch and silicic acid present in said pulp.

15. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit-a hydrate lected from the group consisting of oleic, palmitic, I

stearic, capric, lauric and naphthenic acids and their salts, in a froth flotation treatment, the.

of the metal on the surfaces of said lime-bearing mineral, subjecting such pulp to a froth flotation treatment in the presence of a lauric acid collector reagent to concentrate the magnesite content of the ore in a froth at the surface of the pulp body, and inhibiting flotation of lime-bearing minerals, siliceous matter and gangue in said pulp under the influnce of the collector reagent by having causticized starch and silicic acid present in said pulp. 1 1

16. The method of concentrating magnesite ores, which comprises introducing magnesite ore in finely divided condition into a liquid carrier vehicle to form a pulp, introducing a salt selected from the group consisting of salts of aluminum, tin and iron into said pulp to react with limebearing mineral of the pulp and deposit a hydrate of the metal on the surfaces of said limebearing mineral, subjecting such pulp to a froth of lime-bearing minerals, siliceous matter and gangue in said pulp under the influence of the collector reagent by having causticized starch and silicic acid present in said pulp.

17. In a process for treating magnesite ores for the recovery of magnesite separated from contaminating inclusions, in which magnesite particles of an aqueous magnesite ore pulp are selectively filmed with a collector reagent selected from the group consisting of oleic, palmitic, stearic, capic, lauric and naphthenic acids and their salts, and then the pulp is subjected to froth flotation, the improvement which comprises conditioning the pulp for froth flotation by adding suiiicient caustic to the pulp to produce at least a. pH of 8, and forming a colloidal metallic hydroxide precipitate in the pulp through the introduction of a metallic salt selected from the group consisting of salts of aluminum, tin and iron into the pulp of the type that will reactwith the lime content thereof.

18. In a process for treating magnesite ores for the recovery of magnesite separate from contaminating inclusions, in which magnesite particles of an aqueous magnesite ore pulp are selectively filmed with a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts, and then the pulp is subjected to froth flotation, the improvement which comprises conditioning the pulp for froth flotation by adding sufficient caustic to the pulp to produce at least a pH of 8, and forming a colloidal metallic hydroxide precipitate in the pulp through the introduction of ferric chloride into the pulp.

19. In a process for treating magnesite ores for the recovery of magnesite separate from contaminating inclusions, in which magnesite particles of an aqueous magnesite ore pulp are ,selectively filmed with a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts, and then the pulp is subjected to froth flotation the improvement which comprises conditioning the pulp for froth flotation by adding sufllcient caustic to the pulp to produce at least a pH of 8, and forming a colloidal metallic hydroxide precipitate in the pulp through the introduction of aluminum sulfate into the pulp.

20. In a process for treating magnesite ores for the recovery of magnesite separate from contaminating inclusions, in which magnesite particles of an aqueous magnesite ore pulp are selectively filmed with a collector reagent selected from the group consisting of oleic, palmitic,

stearic, capric, lauric and naphthenic acids and their salts, and then the pulp is subjected to froth flotation, the improvement which comprises conditioning the pulp for froth flotation by forming therein a colloidal metallic hydroxide precipitate ,through the introduction into the pulp of a metallic salt selected from the group consisting of aluminum, tin and iron of the type that will react with the lime content thereof, and a caustic of the type that will give the pulp a pH of at least 8.

21. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble contents of the pulp by aerating said pulp in the presence of; a hydrogel-forming salt selected from the group consisting of aluminum, tin and iron salts; silicic acid; causticized starch: a lime depressantselected from the group consisting of alkali pyrophosphates and sodium lignin sulfonate; and a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts.

22. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such'lime and insoluble content of the pulp by aerating said pulp in the presence of: a hydrogel-forming saltselected from the groupconsisting of aluminum, tin and iron salts; silicic acid, a depressant for the insolubles selected from the group consisting of starch, glues, caramel, and caustic extracts of coal; a lime depressant selected from the group consisting of alkali pyrophosphates and sodium lignin sulfonate; and a collector reagent selected from the group consisting of oleic,. palmitic, stearic, capric, lauric and naphthenic acids and their salts.

23. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite, dolomite and low grade magnesite particles, introducing aluminum sulfate into the pulp to react withthe dolomite particles and form calcium sulfate and a hydrogel, and selectively floating the high grade magnesite away from the dolomite reaction product in an alkaline medium having a pH of at least 8 by aerating the pulp in the presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts.

24. The process of treatingmagnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite and other particles containing calcareous constituents, introducing aluminum sulfate into the pulp to react with the calcareous particles and form calcium sulfate and a hydrogel, and selectively floating highgrade magnesite away from the calcareous reaction product in an alkaline medium having a pH of at least'8 by aerating the pulp in the. presence of a collector reagent selected from the group consisting of oleic, palmitic, stearic, capric, lauric and naphthenic acids and their salts.

25. The process of treating magnesite ores by froth flotation, nesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of: a hydrogel-forming salt selected from the group consisting of aluminum, tin and iron salts; polymerized silicic acid, a

- depressant for the insolubles selected from the which comprises forming a mag-- 

